Method and device for automatically releasing the automatic parking brake when starting

ABSTRACT

A method and a device for automatically releasing an automatic parking brake at start-up. A transmitted torque estimation threshold value is determined that enables the vehicle movement to be balanced. Then, at start-up a loop for calculating the transmitted torque estimation is carried out so long as the calculated value does not exceed the threshold value. When the threshold is exceeded, an automatic parking brake-release command is produced.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention concerns a method and device for automatically releasingthe automatic parking brake when starting.

II. Description of Related Art

In the state of the art, making electric parking brakes which replacemanual parking brakes has previously been proposed.

The electric parking brake is connected to a computer which, dependingon different operating signals of the vehicle, permits its automaticrelease without the driver's direct intervention.

In the state of the art, a system of assistance to starting on a hill,using the automatic parking brake, has also been proposed, which isbased on detection notably of the degree of depression of the clutchpedal, in order to deduce therefrom the engine torque available to thewheel, on the one hand, and for the aid of the driver, on the other, instarting the vehicle, when the latter is maintained on the slope byoperation of the automatic parking brake.

The above system operates correctly.

However, the inventors found that the solution had a rather high costwhich it was desirable to reduce. They realized that eliminating theclutch pedal position detector is a way of reducing that cost.

Along the same lines, in the solution previously developed, use of theinformation on the clutch pedal position has to be converted into atorque value transmitted to the wheel, which notably complicates themeans of calculation of the automatic parking break release controllerwhen the latter is working to assist starting on a hill.

BRIEF SUMMARY OF THE INVENTION

In order to remedy those problems of the state of the art, thisinvention concerns a method of assistance in starting a vehiclecontaining a power unit and an Automatic Parking Break equipped with ameans of executing a command to release or deactivate the parking brake.The method of the invention consists in executing, at least after astarting phase of the power unit:

-   -   A stage of estimation of a transmitted torque value which        balances the vehicle on the slope;    -   A loop consisting in executing an incremental calculation of an        estimation of the torque really transmitted at a given instant,        while the estimation of the torque really transmitted is        insufficient to surpass the estimation of the torque        transmitted; and then    -   A stage of production of a starting or deactivation command of        the Automatic Parking Brake.

According to one aspect of the method, the stage of estimation of atransmitted torque value which balances the vehicle on the slopeincludes a stage for calculating a static model of the vehicle on theslope from a measurement of an angle of inclination delivered by a slopesensor and knowledge of a given value representative of the transmissionspeed.

According to one aspect of the method, the measurement of an angle ofinclination being less than a given threshold, the estimation of atransmitted torque value which balances the vehicle on the slope isincreased by a given value.

According to one aspect of the method, the given value of increase ofthe estimation of a transmitted torque value which balances the vehicleon the slope depends on measurement of the angle of inclination;

According to one aspect of the method, the stage of incrementalcalculation comprises:

-   -   a stage of reading of an effective average torque value        associated with the dynamic state of the power unit;    -   a stage of reading of an engine speed value;    -   a stage of calculation of the time derivative of the engine        speed;    -   a stage of determination of the moment of inertia of the power        unit and of calculation of the load moment in the form of a        product of the moment of inertia of the power unit by the time        derivative of the engine speed;    -   a stage of determination of an estimation of transmitted torque        according to an equation of the form: ECT=Cme−Jmot×dWm/dt.

According to one aspect of the method, there is a stage ofresynchronization of the reading of an effective average torque valueand of an engine speed value, so that each pair of values (Cme, Wm)corresponds to the same time interval.

According to one aspect of the method, it is arranged to add apredetermined delay, preferably equal to three periods of passage to theTop Dead Center of the thermal engine of the power unit, on the value ofresynchronization of the estimated average torque value, in order totake into account notably the waiting time for filling of the manifoldand for ignition.

According to one aspect of the method, the resynchronization stageconsists in applying the resynchronization on the derivative value D_Wmof the engine speed Wm between two samples separated by aresynchronization time notably according to the equation:D_Wm=[Wm(8)−Wm(1)]/time, in which “time” determines theresynchronization period and Wm(1) and Wm(8) the values of beginning andend of the resynchronization period.

According to one aspect of the method, the transmitted torque estimationstage (ECT) comprises the comparison of a transmitted torque estimationvalue (ECT) to a predetermined threshold value (ECTthreshold), so thatif the threshold is exceeded in a test of a counter incremented on eachtransmitted torque estimation stage (ECT) relative to a predeterminedthreshold (Smin_loop_Delay), so that if the threshold on the counter isexceeded, a command authorizing release of the Automatic Parking Brakeis generated.

According to one aspect of the method, the transmitted torque estimationstage ECT further comprises a predetermined offset stage, so as toreduce the disturbing effect of starting and stopping of some secondaryconsumers (Consumers) of energy or power supplied by the thermal engine,by carrying out the operation:ECT _(—) Corr _(—) k=ECT _(—) k+g(Consumers)

so that the range in which the engine can be considered idling and therange during which an offset g(Consumers) on the transmitted torqueestimation can be realized may be determined. According to theinvention, four criteria or tests are carried out simultaneously inorder to arrive at such an offset.

According to one aspect of the method, the offset is effected at theconclusion of a test during which four conditions are combined:Wm≦Smax_Wm_IdleABS(D _(—) Wm)≦Smax_(—) D _(—) M_idleTHETA_Acc≦Smax_acc_idleD_Acc≦0.

Conditions under which:

Smax_Wm_idle represents a threshold value below which the engine speedindicates that the engine is at rest or idling;

Smax_D_M_idle represents a threshold value below which the absolutevalue ABS(D_Wm) of the time derivative of the engine speed D_Wmindicates that the engine is at rest or idling;

Smax_acc_idle represents a threshold value below which the degree ofdepression of the accelerator pedal THETA_Acc indicates that the engineis at rest or idling;

D_Acc represents the time derivative of the degree of depressionTHETA_Acc of the accelerator pedal, which is negative when the driverlifts his foot from the accelerator pedal, so that, if the test isnegative, the control returns to initialization of a counter CPTR, thepower unit being deemed unconnected to the driving wheels,and so that, if the test is positive, the control passes to a test whereone looks whether the counter CPTR is below a predetermined thresholdvalue CPTR_threshold,so that if the test is positive, the control passes to a stage in thecourse of which an initially zero “offset” value, when the counter CPTRis itself initialized at the stage, is increased by the value of thecurrent estimation ECT;

then, the value of the counter CPTR being incremented by one step on astage, the control returns to the test stage;

so that, if the test is negative, the offset value is transmitted to aroutine of calculation of an offset value of the transmitted torqueestimation ECT, an offset value noted “offset_ECT”, which is equal tothe ratio of the “offset” value calculated on the stage to the valueCPTR of the counter which at that time equals CPT_threshold.

According to one aspect of the method, a stage is executed to produce adriver activity report, so that release of the Automatic Parking Brakewill be refused in case of lifting of the accelerator pedal.

According to one aspect of the method, a stage is executed to detect arelease demand when the power unit is not engaged.

According to one aspect of the method, the stage consists, without usingany sensor of depression of the clutch pedal, in detecting the engagedstate by means of two maps of the estimation of torque transmitted as afunction of the degree of depression of the accelerator pedalrespectively established when the wheels are engaged and when the wheelsare disengaged and comparing the value of the estimation of torquetransmitted to each of the map values addressed by measurement of thedegree of depression of the accelerator pedal in order to produce, ifcomparison to the first map is positive, a characteristic report of adisengaged state, and if the comparison to the second map is positive,to produce a characteristic report of an engaged state.

According to one aspect of the method, the stage consists in producing,by use of a sensor of depression of the all-or-nothing clutch pedal, acharacteristic report of an engaged or disengaged state.

According to one aspect of the method, a stage for detecting idlingspeed consists in:

-   -   comparing the information on estimated engine torque Cme to two        functions of estimation of idling speed in positive rotation fp(        ) and in negative rotation fn( );    -   applying to function fp( ) an idle gain G_Cme_PV applied on the        estimated engine torque Cme, an Offset_Cme_PV on the estimated        engine torque value in idle position, and the current value CME        in order to produce a priori an idling speed value in positive        rotation;    -   applying to function fn( ) an idle gain G_Cme_NV applied on the        estimated engine torque Cme, an Offset_Cme_NV on the estimated        engine torque value in idle position, and the current value CME        in order to produce a priori an idling speed value in negative        rotation;    -   comparing the engine speed value (Wm) to determine whether a        positive or negative idling speed is present;    -   authorizing release of the Automatic Parking Brake only if no        idling speed is detected.

According to one aspect of the method, a stage of saturation detectionof the high-speed thermal engine is executed, so that release of theAutomatic Parking Brake is prevented on saturation.

According to one aspect of the method, a stage for producing a“horizontal” starting operation without threshold on pressing theaccelerator pedal consists in:

-   -   producing a parking brake release command on the sole        determination that the transmitted torque estimation ECT is        higher than the predetermined threshold ECTthreshold and, in        particular, without testing a threshold on pressing the        accelerator pedal;    -   initializing a state variable on starting up the vehicle in        order to indicate that the accelerator pedal has not yet been        depressed, the variable being represented by Acc_Was_NonZero=0;    -   reading a variable representative of the state of rest of the        engine (Idle);    -   treating the variable Acc_Was_NonZero so that it stays at “1” as        soon as the accelerator has been pressed and until the Idle        variable returns to “1”;        and then consists in authorizing “horizontal” starting when the        variable Acc_Was_NonZero equals “0” and of testing that the        transmitted torque estimation ECT is higher than a threshold        value ECTthreshold in order to authorize release of the        Automatic Parking Brake and thus ensure starting of the vehicle        keeping it in a certain range of acceleration.

According to one aspect of the method, the “horizontal” startingoperation is extended to a descending starting operation in first gear.

According to one aspect of the method, the “horizontal” startingoperation is extended to a descending starting operation in reversegear.

According to one aspect of the method, an excess pitch detection stageand a stage for preventing release of the Automatic Parking Brake in astarting situation if the pitch of the vehicle applied, for example, bytoo great a movement of the passengers in the vehicle exceeds a certainpredetermined threshold.

According to one aspect of the method, a stage for determining a term ofanticipation of the release command of the Automatic Parking Brakedependent on predetermined anticipation values which consists, uponelaboration of the Automatic Parking Brake release command, in alsoexecuting a stage of measurement of the degree of depression of theaccelerator pedal Teta_Acc, and then measuring a time derivative of thesignal Teta_Acc of the degree of depression, that is, D_Acc, andcomparing that instantaneous derivative value D_Acc with a predeterminedthreshold Threshold_Anticipate, so that if the rate of variation of thedegree of depression D_Acc is greater than a Threshold_Anticipate value,the incrementation loop of the transmitted torque estimation value ECTwill be interrupted before the test is real and in order to produce inadvance the Automatic Parking Brake release command.

The invention also concerns a device to assist on-hill starting of avehicle containing a power unit and an Automatic Parking Brake equippedwith a means of executing a parking brake release or deactivationcommand. The device of the invention essentially contains a computer ofa release command connected to a sensor of the degree of slope on whichthe vehicle is engaged and to a sensor delivering information on thespeed or rate of rotation of the power unit of the vehicle.

The invention is characterized in that the computer contains a means ofestimation of the transmitted torque connected to a first input of ameans of comparison, a second input of which is connected to a means forproducing a transmitted torque threshold value corresponding tomaintenance of the vehicle, so that an output terminal of said means ofcomparison produces a release command addressed to the electric parkingbrake according to the method of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will be betterunderstood by means of the description and attached figures, which are:

FIG. 1: a block diagram representing a device according to theinvention;

FIG. 2: a flow chart representing the principal stages of the method ofthe invention;

FIGS. 3 to 5: diagrams explaining an embodiment making it possible toprepare the calculation of an estimation of the transmitted torque;

FIGS. 6 and 7: means making it possible to elaborate an electric parkingbrake release command;

FIGS. 8 and 9: a means of treating the estimation of the transmittedtorque generated according to the invention;

FIG. 10: a means making it possible to detect an abandonment by thedriver of an attempt to start on a hill;

FIG. 11: a means making it possible to take into account the behavior ofdifferent drivers on a given vehicle;

FIG. 12: a means for detecting a speed of the idle driving engine;

FIG. 13: a means for detecting the speed saturation.

DETAILED DESCRIPTION OF THE INVENTION

On FIG. 1 a device to assist starting on a hill is represented in anembodiment of the invention. The vehicle on which the device and theelectric parking brake are installed contains a bus 1 over which signalspass, emanating from the rest of the vehicle 2, from a power unitcontrol computer 3 and from a braking control computer 4, for example oftype ABS™. The bus 1 is a bus of CAN™ standard in a working example. Thepower unit is composed of a thermal engine coupled to drive wheels by atransmission device containing a gearbox and a clutch which can becontrolled automatically and/or by the driver. In other embodiments thepower unit can contain one or more electric machines with or without athermal engine.

The device to assist starting on a hill cooperates with a computer 5controlling the Automatic Parking Brake 6, which is also connected tothe bus 1. The control computer 5 is equipped, as is known, with a meansof producing an Automatic Parking Brake locking command and with a meansof producing an Automatic Parking Brake release command, said locking orrelease commands being generated on a line of connection 11 to theAutomatic Parking Brake proper. If need be, the control computer 5 isalso equipped with a means of returning to the bus 1 of the vehicleinformation on the state of the Automatic Parking Brake.

The computer 5 controlling the Automatic Parking Brake is connected by asuitable line with a slope sensor 27. In other embodiments, informationon the degree of slope being available on the bus 1, the sensor 27 isreplaced by an equivalent means which picks up that information from thedata flow passing over the bus 1.

The Automatic Parking Brake used in the invention mainly contains anelectric motor 7 which is controlled by an electric motor controller 8,the electric power supply of which is connected to the supply system ofthe vehicle 9 and to ground 10, and the command parameters of which(current, voltage or speed and torque) are transmitted by the commandline 11 coupled to the control computer 5 of the Automatic ParkingBrake.

The electric motor 7 cooperates, as is known, with a suitable reducinggear (not represented), which drives a mechanism 12 schematicallyrepresented on FIG. 1 in the form of a bar mounted on the drive shaft 13and the ends of which bear cables 14 and 15 respectively, which arerespectively connected at their ends to a braking control part 16 for aright wheel and to a braking control part 17 for a left wheel.

When the computer 5 controlling the Automatic Parking Brake produces alocking command, a command activating the electric motor 7 istransmitted by line 11 to the controller 8, which sets the electricmotor 7 in rotation, so that the lever 12 pulls the cables 14 and 15with a given tightening stress.

The moving parts 18 and 19 of the brakes 16 and 17 squeeze the disks 20and 21, so that the Automatic Parking Brake will be tightened.

When the computer 5 controlling the Automatic Parking Brake produces online 11 a command releasing the Automatic Parking Brake, the rotation ofthe electric motor 7 is driven in the other direction and the movingparts 18 and 19 of the brakes 16 and 17 are loosened.

By using the device of the invention, when the vehicle is stopped on aramp, the slope sensor 27 delivers a signal representing the degree ofslope on which the vehicle is stopped.

Furthermore, in a situation of starting on a hill, the power unit of thevehicle produces a torque which is transmitted or not to the wheels,depending on whether the clutch is active or not and depending on afraction subject to the clutch position.

As will be seen presently, the principle of the invention consists indetermining an Automatic Parking Brake release condition, so that thecomputer 5 controlling the Automatic Parking Brake, depending on theslope measured by the sensor 27 and on the engine speed presented on thebus 1, produces a command releasing the Automatic Parking Brake, so thatwith the slope effect being balanced by the engine torque, the vehiclecan be in a starting position as soon as the threshold is exceeded.

On FIG. 2 a flow chart is represented, showing the principle stages ofthe method of assistance upon starting on a hill according to theinvention.

In a stage 30 a power unit start-up stage is created, then notably whenthe vehicle is stopped, with the Automatic Parking Brake locked, a stageof initialization of the computer 5 controlling the Automatic ParkingBrake.

The control then passes to a stage 31 of determination of an estimationof the transmitted torque corresponding to the threshold from which theAutomatic Parking Brake can be released without the vehicle undergoing abackward movement.

The control next passes to a stage 32 in the course of which there arecalculated an estimation of the torque transmitted from the moment ofstarting, on the one hand, and an offset or increase of transmittedtorque which makes it possible to balance the estimation of torquetransmitted from threshold and resulting both from the accelerationaction and the clutch action in the case of a standard vehicle withclutch and accelerator pedal, or by equivalent means in cases ofvehicles of other types.

For that purpose, the control passes to a test 33 where the newestimation value of the transmitted torque calculated on stage 32 iscompared to the threshold value established on stage 31. If the test ispositive, on a stage 34, the computer 5 controlling the AutomaticParking Brake is programmed to produce a release command. If the test isnegative, the calculation of a new estimated transmitted torque value isexecuted on stage 32 and the test resumes on loop.

The stage 31 of calculation of a threshold value on the transmittedtorque estimation is now going to be described. That threshold value isdefined from a static model of the vehicle, as well as on the idea thatthe transmission speed applied by the transmission device insertedbetween the wheels and the power unit is placed on a given transmissionspeed value, like a first gear R1 of a gearbox with multistage speeds.

In other embodiments the device for assisting starting on a hillcooperates with a means of detection of the transmission speed and, inparticular, for a transmission with multistage speeds, a means ofdetection of the position of the gear lever, in order to detect whetherthe vehicle is placed in reverse or in other transmission speeds, whichmakes it possible to increase the sensitivity of the assistance devicedepending on detection of the driver's intention, if it is desired tostart in speeds other than first.

By designating with p the transmission speed, R the wheel radius, α theslope on which the vehicle is located, M the weight of the vehicle and gthe gravitation constant, the threshold value of the transmitted torqueestimation is defined by a product of terms of the form:ECT _(threshold) =M*g*sin(α)*p

The threshold value thus calculated indicates the torque it is necessaryto apply to the wheel so as to keep the vehicle in balance on the slope.It is clear that from this threshold value, any increase of transmittedtorque would enable the vehicle to start. It is therefore possible toproduce from this threshold value a parking brake release command.

The method and device for assisting starting on a hill according to theinvention thus make it possible, through an estimation of transmittedtorque, to make the vehicle start on a hill without any intervention bythe driver on the parking brake control, on the one hand, and withoutany backward movement of the vehicle on starting, on the other.

In an embodiment it was observed that when the slope sensor produced avery low degree of slope α, that is, when the hill is not very steep,the assistance device finds a threshold value of the estimation oftransmission torque ECT_(threshold) very close to 0, and the vehiclethen, when the brake is released, can be set in motion parasitically.

To avoid this situation, an increment value f is added, which depends onthe slope values detected and which, when the slopes are slight, makesit possible to increase the threshold value of the estimation oftransmitted torque. In this embodiment the computer 5 contains a meansfor determining whether the degree of slope is less than a given valueand, on the positive response of this determination, to add to thedetermination of the already described means of the threshold value ofthe estimation of transmitted torque ECT_(threshold) a term determinedas a function of the degree of slope α, that is, f(α). In an embodimentthe calculation module of the threshold value of the transmitted torqueestimation therefore further includes a map memory which contains aplurality of addresses, one for each discrete value produced by asuitable slope sensor, and each address containing a numerical valuerepresenting the supplementary value to be added to the transmittedtorque threshold when the degree of slope α is slight, and a moduleadding said supplementary value read on the map memory with the valuepreviously calculated from the static data representing the statics ofthe vehicle on the slope and in order to produce a corrected value ofthe estimation of transmitted torque threshold of equilibrium.

In one particular embodiment the term f(α) is also valid outside slightslopes in order to add approval of driving and/or of safety. Its effectis then to secure the vehicle somewhat more on starting.

In order to execute stage 32 of the method of the invention, thecomputer 5 controlling the Automatic Parking Brake contains:

-   -   a first reading module of the effective average torque Cme        supplied by the computer of the engine 3 in the form of        information circulating on the bus 1 of the vehicle,    -   a second reading module of the instantaneous speed Wm of        rotation of the thermal engine supplied by the computer of the        engine 3 in the form of information circulating on the bus 1 of        the vehicle,    -   a third module making it possible to calculate the time        derivative dWm/dt of the rate of rotation on output of the power        unit from the datum of rate of rotation or engine speed        retrieved by the second module;    -   a fourth module for calculating the product of a value of the        moment of inertia Jmot characteristic of the inertia of the        engine, as well as the output value of said third module;    -   a fifth module for subtracting the output value of the fourth        module, presented at a subtraction input of the fifth module,        from the output value of the said first module, so that on its        output an instantaneous value of the instantaneous estimation of        transmitted torque produced is presented according to an        equation: ECT=Cme−Jmot×dWm/dt.

On FIG. 3 a diagram is represented, which explains a cause of error onthe estimation of transmitted torque and on the engine speed.

In the upper part of FIG. 3, a timing diagram 40 is represented, showingsuccessive fields 41 and 42 corresponding to referenced periods #T and#T+1. At the end of each of these fields, a set of transmitted data isavailable on the different receivers.

In each field the member data are structured according to a protocolregistered by a protocol control circuit on the CAN bus in numeric wordsrepresenting values of parameters transmitted on the bus and insertedwith different phases and periodicities.

Thus, in the example illustrated on FIG. 3, on field 41 of period #T, afirst word Cme_(T) of a first variable transmitted and a second wordWm_(T) of a second variable transmitted will both be available at theend of field #T. But, because of periods T1 and T2 for the first andsecond words transmitted different from and/or greater than the periodof the field, or also because the latter varies, only the first wordCme_(T+1), is available at the end of field #T+1. The second wordprovided for field T+1 is received on a subsequent field 43 under theword Wm_(T+1).

In the invention it is necessary for the computer 3 controlling thepower unit (see FIG. 2) to produce:

-   -   an estimated value of the estimated average torque, inscribed in        the form of a numeric word Cme on the CAN bus; and    -   an engine speed value inscribed in the form of another numeric        word Wm on the CAN bus.

Owing to the mechanisms of production of each of those two values andthe fact of occupation of the transmission field according to the CANbus protocol, as a result, on a given date t, the computer controllingthe Automatic Parking Brake FPA 5 for executing a command 11 to releasethe Automatic Parking Brake in a situation of starting on a hill doesnot receive at the same time the two data corresponding to the same dateand necessary, which prevents a proper estimation.

To remedy that problem, the invention proposes a means of making acorrection on the values Cme of the estimated average torque and Wm ofthe engine speed, as well as a resetting of the information available asa function of a flow of this data according to the fields transmitted onthe CAN 1 bus.

On FIG. 4 a means of calculation of the estimation of transmitted torque50 transmits an instantaneous value of the estimated average torque Cmeto a writing module 51 on the CAN 1 bus, so that, at given moments, aninstantaneous value of the estimated average torque speed will beavailable on the CAN 1 bus.

Furthermore, a calculation module 52 of estimation of the engine speedWm is connected to an input of the writing module 51 on the CAN 1 bus,so that, at given moments, a value of estimation or measurement of theengine speed will be available on the CAN 1 bus.

For that purpose, information relating to a particular state of thethermal engine, like the instant of top dead center t_(PMH), is suppliedto suitable inputs of modules 50 and 52, so as to synchronize thecalculations of the first word Cme and second word Wm.

A controller 53 of exchanges on the CAN 1 bus receives information frommodules 50 and 52, according to which a new datum is available, thewriting module 51 being connected to the controller 53 in order tonotify it of a writing operation on the CAN 1 bus and a controlleroutput of the controller 53 being connected to a writing authorizationinput on the CAN 1 bus of module 51.

The writing module 51 on the CAN 1 bus thus generates a data field as afunction of the multiple data it injects on the CAN bus.

The thermal engine represented by reference 54 is coupled to a top deadcenter sensor 55 in order to generate on its output 56 informationt_(PMH) of the top dead center the instant the latter appears.

A reading module 57 on the CAN bus is arranged to receive a readingcommand through a connection 58 to the CAN bus controller 53 andcompletes on a line 59 the end of reading of a field.

An output 60 of the reading module 57 makes it possible to transmitrespectively to a register 61 the successive values of estimation of theestimated engine torque decoded on the fields received by module 67 andto a register 62 the successive values of engine speed Wm decoded on thefields received by module 67.

The control circuit 53 of the CAN bus contains command outputs,respectively a command output 63 connected to a reading authorizationinput of the engine speed register 62 and a command output 64 connectedto a reading authorization input of the register 61 of transmittedtorque estimations, so that the respective outputs 65 of register 61 and66 of register 62 are connected to the proper inputs of aresynchronization circuit 67, which makes it possible at every instantto maintain a value corrected as a function of the indication of theinstant of top dead center t_(PMH) supplied by the output 56 of thesensor 55, of the respective instantaneous values 68 of the estimatedaverage torque and 69 of the engine speed.

The resynchronization circuit 67 has a memory containing a table on acycle of pairs of output data, so that the serial number of a valuerepresenting the first word received on its first input is associatedwith a serial number of a value representing the serial number of asecond word received. The resynchronization circuit 68 also containsregisters of sequences of successive values of the first word and/or ofthe second word and a means, dependent on associations of serial numbersof the aforesaid memory, for applying on output a pair of a first wordand a second word corresponding to one and the same moment ofcalculation. The pair of resynchronized words is then presented onoutputs 68 and 69.

On FIG. 5 an embodiment of a synchronization circuit 67 is represented,which works essentially on the engine speed and makes it possible to usean offset in the mechanism making pairs of words (Cme, Wm) available,corresponding to a characteristic effect on acceleration of the thermalengine, a situation which always occurs when the vehicle is kept on theslope with the Automatic Parking Brake locked.

At the input terminal 65 of the module 67 for synchronization of thedata on the CAN 1 bus, the writing input of a synchronization register70 of the transmitted torque estimation was connected.

For that purpose, a sequencer 71 receives via a suitable input thesignal indicating top dead center 56 and transmits writing commands on aline 72 and reading commands on a line 73 directed to writing andreading terminals of the register 70. In the case of a reading signal,the signal corresponds to the engine speed with an offset of a periodproportional to the engine speed. That measurement makes it possible torender the information refresh time on the engine speed a function ofthe value of the engine speed itself.

At a resynchronization moment predetermined relative to the availabilityindicated on line 72, reading line 73 transmits the value maintained inregister 70 to a register 74. Register 74 permanently presents at itsoutput 68 an available value of estimation of the synchronizedtransmitted torque.

The input terminal 56 of the resynchronization module 67 is connected tothe input of a batch 76 of registers in which a plurality of successivevalues of the engine speed Wm acquired at successive instants on the CAN1 bus is maintained.

For that purpose, a sequencer 71 contains two writing and readingcommand outputs 77 and 78 respectively, which make it possible tomaintain the plurality of values by placing the most up-to-date value onthe first address noted “1” in the batch 76 and by pushing downward thevalues contained in the following registers of the batch 76.

A subtracting circuit 79 contains:

-   -   a positive input connected to a reading output of the batch 76        on which the oldest value of the engine speed Wm kept in the        batch 76 is available, and    -   a negative input to which is connected the most recent value of        the engine speed also available on the input terminal 66 of the        module 67.

An input 80 of the subtracting circuit 79 receives a representative“time” value of the time elapsed on acquisition between the oldestvalue, like the eighth value “8”, noted Wm(1) and received in oneparticular working example, and the most recent value “1” noted Wm(8),so that a value representing a corrected estimated value of the enginespeed is available at the output 81 of the subtracting circuit 79.D _(—) Wm=[Wm(8)−Wm(1)]/time.

The calculated value available at the output of circuit 79 is loaded ina register 82, so that a value of the time derivative of thesynchronized engine speed D_Wm_(sync) is available at its output 83.

The reading and writing of the registers 74 and 82 are carried out underthe control of the sequencer 71, which respectively presents a writingcommand line 84 and a writing command line 85.

The writing command is carried out under the control of the sequencer71, which manages a register 86 in which a time offset or delay value ΔTis registered, which corresponds to a desired delay in transmission ofvalues synchronized with the rest of the estimator, so that one can takeinto account notably:

-   -   the time of filling of the manifold of the thermal engine, and    -   the time of ignition when the thermal engine is in acceleration        phase, as is the case of on-hill starting.

In a working example the inventors found the best effect when a delay ΔTwas applied equivalent to three successive Top Dead Centers beforestarting synchronization and transfer of the pairs of the first Cme andsecond Wm or D_Wm words of resynchronized values.

On FIG. 6 one particular embodiment of the method of the invention isrepresented. The method of the invention consists, upon an initial phaseS0, in resynchronizing the data concerning the engine speed and theestimated average torque, calculating the threshold value of thetransmitted torque estimation, as described by means of the flow chartof FIG. 2, then repeating the test that the estimation of transmittedtorque calculated on the given date is higher than the thresholdECT_(threshold) for at least a predetermined number of samplesSmin_Loop_delay.

For that purpose, the counter CPTR is set at an initial value 0 on astage S1, then the control passes to a standby test S2 of a value ECT_krepresenting the estimation calculation of the torque transmitted.

When that value is available, the control passes to a stage S3 ofincrementation of the counter CPTR and then to a test S4 of estimationof the transmitted torque ECT_k relative to the thresholdECT_(threshold).

If the test is negative, the control returns to initialization of thecounter CPT=0 of stage S1.

If test S4 is positive, the control passes to a test S5 where one lookswhether the counter CPTR has reached its maximum value Smin_Loop_delay.

If the test is positive, the control passes to a stage S6 in the courseof which the computer 5 for control of the Automatic Parking Brake FPAgives a command authorizing release of the parking brake.

If the test S5 is negative, the control returns to the input of test S2pending arrival of the sample following estimation of the transmittedtorque ECT_k.

On FIG. 7 an embodiment of a means of calculation of the computer 5implementing the flow chart of FIG. 6 is represented. That means ofcalculation of the computer 5 includes a counter 90 which maintains anumeric value CPTR and updates it on each event presented at its inputnoted “+” by increasing it by a predetermined value like “1”. The valueCPTR of the counter 90 is then available on a reading output terminal.

The means of calculation of the computer 5 contains an input 91 on whichthe value ECT_k is loaded and which is connected, on the one hand, tothe input of a circuit 93 detecting the arrival of a value ECT_k, and toa first input of a comparator 92.

The detection output of the module 93 for detection of arrival of asample ECT_k is connected to the incrementation command input ‘+’ of thecounter 90, the reading output terminal of which is connected to a firstinput of a comparator 93.

A threshold value ECTthreshold, maintained in a register 94, istransmitted to a second input of comparator 92.

The comparator 92 contains a first output 96 and a second output 95,complementing one another, so that if the test carried out by thecomparator 92 is positive, the first output 96 passes to the activestate and is connected to a first input of an AND gate 97, while thesecond output 95 passes to the inactive state and is connected to aninput terminal for reset to an initial value like the value ‘0’ of thecounter 90.

The counting value CPTR available in the counter 90 is transmitted to afirst input of a second comparator 98, a second input of which isconnected to a register 99 maintaining the maximum counting value, atthe end of which the release authorization can be executed.

For that purpose, when the test carried out by the second comparator 98is positive, its output passes to the active state and is connected to asecond input of the AND gate 97, so that the output 100 of the AND gate97 passes to the active state to indicate an authorization of release ofthe Automatic Parking Brake.

In one particular embodiment the value Smin_Lop_Delay loaded in theregister 99 is determined as a function of the period of sampling orloop rate of the algorithm of FIG. 6 and of the time or delay desiredbetween the first overshooting by the estimated transmitted torque valueECT of the threshold value ECT_(threshold) and execution of the releasecommand of the parking brake FPA. According to the invention, theregister 99 contains a means of writing of a value so determined ofSmin_Lop_Delay, which is activated on initialization of the vehicle orelse on its manufacture or on its maintenance with a production toolknown to the expert, or else on detection of one type of driver made bymeans of the vehicle's computer 1 which transmits over the bus 1 acharacteristic value of Smin_Lop_Delay associated with the driverdetected, for example, by means of the ignition key or of the type ofdriver according to an algorithm of the type of driving carried out bythe driver.

In another particular embodiment not represented in the drawings, thetransmitted torque estimation value ECT received at the terminal 91 ofthe module of FIG. 7 further receives an offset predetermined so as toreduce the disturbing effect of starting and stopping by some secondaryconsumers of energy or power supplied by the thermal engine. Such anoffset is carried out upstream from the circuit 91 of detection andinput of the comparator 92 by means of an adder which performs theoperation:ECT _(—) Corr _(—) k=ECT _(—) K+g(Consumers)

The method of the invention provides a means for determining the rangein which the engine can be considered idle and the range during which anoffset g(Consumers) on the transmitted torque estimation can berealized. According to the invention, four criteria or tests areperformed simultaneously in order to arrive at such an offset.

On FIG. 8 a flow chart of the method of the invention is represented.The offset calculation entry point 101 makes it possible, on a stage102, to place a particular counter CPTR at an initial value like value0. The control then passes to test stage 103 in the course of which fourconditions are combined:Wm≦Smax_Wm_IdleABS(d _(—) Wm)≦Smax_(—) D _(—) M_idleTHETA_Acc≦Smax_acc_idleD_Acc≦0.

Conditions under which:

Smax_Wm_idle represents a threshold value below which the engine speedindicates that the engine is at rest or idling;

Smax_D_M_idle represents a threshold value below which the absolutevalue ABS(D_Wm) of the time derivative of the engine speed D_Wmindicates that the engine is at rest or idling;

Smax_acc_idle represents a threshold value below which the degree ofdepression of the accelerator pedal THETA_Acc indicates that the engineis at rest or idling;

D_Acc represents the time derivative of the degree of depressionTHETA_Acc of the accelerator pedal, which is negative when the driverlifts his foot from the accelerator pedal.

If the test 103 is negative, the control returns to initialization 102of the counter CPTR. The power unit is deemed unconnected to the drivingwheels.

If the test 103 is positive, the control passes to a test 104 where onelooks whether the counter CPTR is below a predetermined threshold valueCPTR_threshold.

If the test 104 is positive, the control passes to a stage 105 in thecourse of which an initially zero “offset” value, when the counter CPTRis itself initialized at stage 102, is increased by the value of thecurrent estimation ECT.

Then, the value of the counter CPTR is incremented by one step on astage 106 and the control returns to the test 103 stage,

If the test 104 is negative, the offset value is transmitted to aroutine 107 of calculation of an offset value of the transmitted torqueestimation ECT, an offset value noted “offset_ECT”, which is equal tothe ratio of the “offset” value calculated on stage 105 to the valueCPTR of the counter which at that time equals CPTR_threshold.

On FIG. 9 an embodiment of a device using the method of the flow chartof FIG. 8 is represented.

The circuit of FIG. 9 contains three input registers, respectively:

-   -   register 110 of the instantaneous engine speed value Wm,    -   register 111 of the degree of depression of the accelerator        pedal in a variable THETA_acc,    -   register 112 which maintains the instantaneous value of        estimation of the transmitted torque ECT.

Register 110 contains a reading output connected respectively to a firstinput of a comparator 113, a second input of which is connected to aregister 114 which maintains a higher threshold value Smax_Wm_idlerepresenting the starting speed limit.

Register 110 is also transmitted to an input of a circuit 115 forcalculation of the derivative D_Wm of the rate of rotation or enginespeed W_m, where one output, on which the absolute value of the timederivative of the engine speed is maintained, is connected to a firstinput of a comparator 116, a second input of which is connected to thereading output of a register 117, in which the threshold value ofvariation or time derivative of the engine speed Smax_D_Wm_idle ofvehicle starting is maintained.

Register 111, which maintains the angle of depression or stepping on theaccelerator pedal THETA_acc, is connected to a first input of acomparator 118, a second input of which is connected to the readingoutput of a register 119 in which a threshold value Smax_acc_idle isregistered, corresponding to a maximum degree of depression of theaccelerator pedal in a vehicle starting situation.

The value THETA_acc is also transmitted to a circuit 120 of calculationof the time derivative of depression of the accelerator pedal D_acc, anoutput of which is transmitted to a first input of a comparator 121.

A second input of the comparator 121 is connected to the reading outputof a register 122, in which a threshold value of the acceleration shiftis maintained as a zero or roughly zero value so as to detect asituation in which the driver maintains the depression of theaccelerator pedal in stable position.

The outputs of the four comparators 116, 113, 118, 121 are connected tothe corresponding inputs of an AND gate 124, the output of which isconnected to an incrementation input of a counter 129, the outputcounting value 130 of which is connected respectively to a first inputof a comparator 131 and to an input terminal of a buffer circuit 132.

The second input of the comparator 131 is connected to the readingoutput of a register 133 in which a maximum counting value is registeredfor the counter CPTR.

The output of the counter 131 is connected to a control terminal 134 ofthe buffer circuit 132, so that an output terminal 135 of the buffer 132copies out the value presented to its input 130 when the controlterminal 134 is in high state, and transmits it to a denominator inputof an arithmetic divisor circuit 136.

Register 112, which maintains the instantaneous value of estimation ofthe transmitted torque ECT, is supplied to a first input of an adder137, a second input of which is connected to the reading output of aregister 138 maintaining a partial accumulated sum value.

A writing input 139 of register 138 is connected to the instantaneousaddition output 140 of the adder 137, so that at every instant register138 contains a cumulative value of successive values of estimation oftransmitted torque ECT_k during positive evolution of the counter CPTR129.

The output 140 of the adder 137 is also connected to a numerator inputof the arithmetic divisor circuit 136 so that, when the output signal134 of the comparator output passes to the high state, the valueaccumulated by the adder 137 is divided by the value of the counter 129and so that this cumulative value is supplied on output to a register141 maintaining a transmitted torque estimation value with offsetaccording to the principle of the algorithm of FIG. 8.

On FIG. 10 another circuit is represented, which uses an arrangement ofthe invention making it possible, by means of the information suppliedby the sensor of degree of depression of the accelerator pedal, toproduce information concerning the activity of the driver.

In one embodiment the circuit measuring the activity of the driver inthe invention makes it possible to reject release of the parking brakein case of lifting of the accelerator pedal. In such a situation,lifting of the accelerator pedal can be considered as indicating thedriver's abandonment of the effort to start.

In another embodiment, a filtering of too marked a rise of theaccelerator pedal is added, considering that the detection of a timederivative of the angle of depression of the accelerator pedal is ameasurement of a first starting action of the engine.

For that purpose the device of the invention contains a register 150 inwhich is maintained the instantaneous value of time derivative D_Acc ofthe degree of depression THETA_Acc of the accelerator pedal produced bymeans of the aforesaid circuit 120 on FIG. 9.

The reading value of register 150 is transmitted to the first inputs oftwo comparators, 151 and 152 respectively, the second inputs of whichare respectively connected to reading outputs of registers 153 and 154.Register 153 maintains a lower threshold value Smin_D_Acc_TakeOff,characteristic of an upper limit of rate of depression of theaccelerator pedal. If the time derivative D_Acc is less elevated thanthe registered value, the comparator 151 produces an active value at itsoutput, which is transmitted to a first input of an AND gate 155.Likewise, if that time derivative D_Acc is less than or equal to a lowerthreshold value Smax_D_Acc_TakeOff, registered in register 154, thecomparator circuit 152 passes to the active state and places its outputconnected to the second input of the AND gate 155 at the active value.

The output of the AND gate 155 is connected to a first input of a secondAND gate 156, a second input of which is connected to the outputterminal 100 of the circuit of FIG. 7. The authorization to release theAutomatic Parking Brake is then presented to the output 157 of thecircuit of FIG. 10 if the output of the AND gate 155 is active at thesame time as the output terminal 102.

The invention also provides a means of detecting a hillside startingdemand when the engine is not engaged, without, however, the presence ofa sensor of degree of depression of the clutch pedal or of the state ofengagement.

For that purpose, according to the invention, two maps 163 and 164respectively representing the degree of depression of the acceleratorpedal and the transmitted torque estimation are made upon initializationof the computer. The bases of these two maps make it possible toestablish whether the engine is disengaged from the driving wheels orwhether the thermal engine is mechanically connected to the drivingwheels.

For that purpose, several maps can be loaded, as a function notably ofthe type of driver entered in a driver identification register, or as afunction of the type of vehicle when the circuit of the invention isintended to equip different vehicles of a line of the same manufacturer.

The circuit of the embodiment of FIG. 11 essentially contains two accessregisters, namely:

-   -   a register 160 for maintaining the instantaneous value of the        degree of depression of the acceleration pedal THETA_Acc, and    -   a register 161 for maintaining the instantaneous value of        estimation of the transmitted torque ECT.

Furthermore, a module 162 for detection of the identification of thedriver and/or of the vehicle makes it possible to determine what map touse on executing the method of the invention. The circuit or module 162for detection of the identification of the driver and/or vehiclecontains a control output line which is connected to respective controlinputs 165 and 166 of a first map memory 163 and of a second map memory164. The first map memory 163 contains a list of threshold values of thedegree of depression of the accelerator pedal, which makes it possibleto distinguish whether the driver is in engagement phase or not, thatthreshold value being determined by detection of the type of driverand/or vehicle of module 162.

The second map memory 164 contains a threshold value from which thevehicle can be considered engaged on the transmitted torque estimationCT. For that purpose, the registers 160 and 161 are connected to firstinputs of a first comparator 167 and a second comparator 168, the secondinputs of which are respectively connected to output 169 of the firstmap memory 163 and output 170 of the second map memory 164. The outputsof the two comparators 167 and 168 are connected to inputs of an ANDgate 171, the output of which is connected to a release command 172.

The release command 172 can be combined with the release command comingfrom the output 157 of the circuit of FIG. 10 and/or from the output 100of the circuit of FIG. 7.

In part B of FIG. 11 the diagrams of evolution of the transmitted torqueestimation ECT is represented in ordinates as a function of the angle ofdepression THETA_Acc of the accelerator. The transmitted torqueestimation is roughly constant at a very low value in the direction ofrotation of the engine along a curve C1, when the power unit is idle,that is, when the clutch is not activated. The curve of evolution of thetransmitted torque estimation ECT is represented by line C1 and, ingeneral, involves a range of values not dependent on the angle ofdepression of the accelerator of several Newton-meters.

In a second type of curve like curve C2, from a threshold SO ofdepression of the accelerator pedal, the transmitted torque estimationincreases very rapidly. Thus, it is possible to determine a threshold S1from which one can begin testing the transmitted torque estimation and athreshold S2 of transmitted torque above which one can be sure that thethermal engine is engaged on the driving wheels of the vehicle.

Those values S1 and S2 are respectively registered in the first mapmemory 163 and the second map memory 164 according to the type ofvehicle or type of driver or identification thereof for a given vehicle.

On FIG. 12 a means making it possible to detect idling speed when thevehicle is idling is represented.

The principle of that part of the invention consists in using theestimated engine torque information Cme and integrating the informationin order to estimate the speed of the power unit and to determinewhether it is idling. The estimated idle speed Wm_0 can then be comparedto the real engine speed Wm and if it remains less than the idle speedWm_0, it can be deduced that the vehicle is not in idle and a releasecan then be authorized.

In one embodiment the circuit of FIG. 12 contains an input register 180in which an estimated engine torque value Cme produced on the enginecomputer is maintained. The estimated engine torque value 180 istransmitted to first inputs of two modules, 181 and 182 respectively, inwhich two respective functions are performed, fp( ) estimation of idlespeed in rotation with a positive estimated engine torque CME and fn( )estimate of idle speed in rotation with a negative estimated enginetorque CME.

Module 181 makes it possible to estimate an idle speed value accordingto the estimated engine torque Cme presented at the terminal or register180 and according to a pair of parameters estimated in advance throughsuccessive idle acceleration tests on a sampling of vehiclescorresponding to the type of vehicle on which the device of theinvention is mounted. In a first register 183 a gain applied to theestimated engine torque is registered, that is, the value G_Cme_PV inidle. In a second register 184 an offset on the estimated engine torquevalue in idle position is registered, that is, Offset_Cme_PV. Thefunction fp( ) registered in the calculation module 181 uses the threearguments Cme of register 180, G_Cme_PV of register 183 andOffset_Cme_PV of register 184.

At the output terminal 185 of the calculation module 181 of function fp() an estimated idle speed value W_vide_p [W_idle_p] equal to a givenvalue of function fp( ) applied to the three input arguments 180, 183and 184 is presented according to the equation:W _(—) vide _(—) p=fp(G _(—) Cme _(—) PV, Offset_(—) Cme _(—) PV, Cme).

In one particular embodiment, the function fp( ) is defined by theequation:W _(—) vide _(—) p=G _(—) Cme _(—) PV×Cme+Offset_(—) Cme _(—) PV.

Module 182 makes it possible to estimate an idle speed value accordingto the estimated engine torque Cme presented at the terminal or register180 and according to a pair of parameters estimated in advance throughsuccessive idle acceleration tests on a sampling of vehiclescorresponding to the type of vehicle on which the device of theinvention is mounted. In a first register 186 a gain applied to theestimated engine torque Cme is registered, that is, the value G_Cme_NVin idle. In a second register 187 an offset on the estimated enginetorque value in idle position is registered, that is, Offset_Cme_NV. Thefunction fn( ) registered in the calculation module 181 uses the threearguments Cme of register 180, G_Cme_NV of register 186 andOffset_Cme_NV of register 187.

At the output terminal 188 of the calculation module 182 of function fn() an estimated idle speed value W_vide_n [W_idle_n] equal to a givenvalue of function fn( ) applied to the three input arguments 180, 186and 187 is presented according to the equation:W _(—) vide _(—) n=fn(G _(—) Cme _(—) NV, Offset_(—) Cme _(—) NV, Cme).

In one particular embodiment, the function fn( ) is defined by theequation:W _(—) vide _(—) n=G _(—) Cme _(—) NV×Cme+Offset_(—) Cme _(—) NV.

The circuit of FIG. 12 then contains a register 189 in which theinstantaneous value of the engine speed is maintained and which issupplied to first inputs, of a first comparator 190 and of a secondcomparator 191 respectively, the second inputs of which are respectivelyconnected to the output 185 of module 181 and to the output 188 ofmodule 182. The comparators 190 and 191 switch and pass to the activestate when the engine speed is less than the estimated values ofW_vide_n or W_vide_p, according to the type of speed in progress on thethermal engine of the vehicle. The outputs of the comparators 190 and191 are connected to first inputs of AND gates 192 and 193, the secondinputs of which are respectively connected to the reading output of aregister 194 in which an active value of release of the AutomaticParking Brake of the invention is maintained. The outputs of the ANDgates 192, 193 are connected to inputs of an OR gate 195 the output ofwhich is placed on an output register which maintains a release value ondetection of idle speed.

On FIG. 13 an embodiment of a circuit for executing a stage of themethod of the invention is represented. On development of the invention,the inventors recognized that the injection system equipping the thermalengine of the power units, on high speeds, that is, when the rate ofrotation of the engine is high, might be cut off suddenly. Now, themodule which is associated with the power unit and transmits to the bus1 the estimated average torque value Cme used on the computer of theinvention to elaborate the release command becomes erroneous. In thatsituation, the method of the invention consists in replacing the valuerepresenting the estimated average torque Cme of the thermal engine witha particular correction value on saturation.

For that purpose, the circuit of FIG. 13 contains an input terminal Wmotwhich receives a value representing the speed and a register 200maintaining a threshold value Smax_Wm_saturation beyond which cutoff ofthe injection system can take place.

Both of the said values are transmitted to the input terminals of acomparator 201, the output of which is connected to the input 204 of aswitching circuit 203, a first input terminal 205 of which receives avalue representing the estimated average torque Cme coming from thecomputer associated with the power unit and a second input terminal ofwhich is connected to a corrected estimated average torque value onspeed saturation. When the output terminal of the comparator 201 passesto the active stage because the engine speed has exceeded the prefixedthreshold of the register 200, the correction value of register 202 ispresented at the output 206 of the switching circuit 203 rather than thevalue Cme.

The method of the invention can also include extra options. Inparticular, the method of the invention finds an application in thesituation of a horizontal start, the vehicle being stopped on ahorizontal terrain. Such an operation can be implemented by means of thedevice of the invention on configuration of the vehicle on production,maintenance or on detection of the type of driver or of the driver whenthe latter sits down in the vehicle.

The “horizontal” character of the terrain is defined by a test todetermine whether the signal representing measurement of the angle ofslope is less, in absolute value, than a threshold of angle ofinclination or slope noted Smin_Slope_NonZero, said threshold beingregistered in an angle of slope threshold register, and said signalbeing produced by the slope sensor 27 (FIG. 1).

In that operation the method of the invention consists in producing arelease command of the parking brake on the sole determination that thetransmitted torque estimation ECT is higher than the predeterminedthreshold ECTthreshold and, in particular, without testing a thresholdon stepping on the accelerator pedal, as is required on starting on ahill, as described above.

For that purpose, the method of the invention consists in initializing astate variable on starting the vehicle to indicate that the acceleratorpedal has not yet been depressed, the variable being represented byAcc_Was_NonZero=0.

In the course of execution of the method of the invention, if the“horizontal” starting operation is implemented, a variable representingthe state of rest of the engine, a variable represented by Idle, is inthe False state (“0”) when one of the following four conditions alreadydescribed at least is not true:Wm≦Smax_Wm_IdleABS(D _(—) Wm)≦Smax_(—) D _(—) M_idleTHETA_Acc≦Smax_acc_idleD_Acc≦0.

And which then passes again to the True state (“1”) when the fourconditions are present.

According to the method of the invention, the variable Acc_Was_NonZeroremains at “1” as soon as the accelerator is pressed and until the Idlevariable returns to “1”. The method of the invention then consists ofauthorizing “horizontal” starting when the variable Acc_Was_NonZeroequals “0”,

It is then sufficient to test that the transmitted torque estimation ECTis higher than a threshold value ECTthreshold in order to authorizerelease of the Automatic Parking Brake and thus ensure starting of thevehicle by keeping it in a certain range of acceleration.

The circuit of the device of the invention using the “horizontal”starting operation essentially comprises:

-   -   a circuit for activating the horizontal starting operation on        configuration of the vehicle on production, maintenance or on        detection of the type of driver or of the driver when the latter        sits down in the vehicle, which produces a logic signal at “0”        if the operation is not implemented and at “1” if the operation        is implemented;    -   a “horizontal” position detection circuit in order to detect        that the signal representing the angle of inclination produced        by the slope angle sensor 27 is at absolute value less than a        threshold value registered in a suitable register and        representing the “horizontal” position limit;    -   a first AND gate to combine the output signals of the circuit        for activating the horizontal starting operation and the        “horizontal” position detection circuit;    -   a circuit for elaborating the variable Acc_Was_NonZero which        comprises a comparator of the degree of depression of the        accelerator pedal at a very low predetermined depression        threshold and a reset circuit as soon as the Idle variable        coming from the rest of the starting device of the invention        returns to “0”;    -   a circuit to test the value of the transmitted torque estimation        ECT coming from the rest of the starting device of the invention        at a threshold value ECTthreshold and to produce a release        command of the Automatic Parking Brake;    -   a second AND gate for combining the “horizontal” release command        coming from the circuit to test the value of the transmitted        torque estimation ECT at the output for the first AND Gate and        the output of which is connected to the electric motor        controller of the Automatic Parking Brake.

The horizontal release operation without accelerator offers animprovement of comfort of the starting operation of the parked vehicle.Without acceleration, starting takes place more slowly and comfort isimproved.

In a first variant the “horizontal” starting operation is extended tothe case of starting on descent in first gear.

For that purpose, the “horizontal” starting operation is also activatedwhen a negative slope is detected and first gear is engaged.

For that purpose, the device of the invention contains:

-   -   a circuit for activating the starting operation “on descent in        first gear,” upon configuration of the vehicle on production,        maintenance or upon detection of the type of driver or of the        driver when the latter sits down in the vehicle, which produces        a logic signal at “0” if the operation is not implemented and at        “1” if the operation is implemented;    -   a circuit for detection of “descent in first gear,” in order to        detect that the signal representing the angle of inclination        produced by the angle of slope sensor 27 is less than a negative        threshold value registered in a suitable register and        representing the limit of “descent in first gear”;    -   a third AND gate for combining the output signals of the circuit        for activating the starting operation “on descent in first gear”        and of the circuit for detection of “descent in first gear”;    -   a fourth AND gate for combining the output of the third AND gate        and the output of the circuit for testing the value of the        transmitted torque estimation ECT coming from the rest of the        starting device of the invention at a threshold value        ECTthreshold and for producing a release command of the        Automatic Parking Brake “on descent in first gear”.

In a second variant the “horizontal” starting operation is extended tothe case of starting on descent in “reverse”.

For that purpose, the “horizontal” starting operation is also activatedwhen a positive slope is detected and the reverse gear is engaged.

For that purpose, the device of the invention contains:

-   -   a circuit for activating the starting operation “on descent in        reverse gear,” upon configuration of the vehicle on production,        maintenance or upon detection of the type of driver or of the        driver when the latter sits down in the vehicle, which produces        a logic signal at “0” if the operation is not implemented and at        “1” if the operation is implemented;    -   a circuit for detection of “descent in reverse gear”, in order        to detect that the signal representing the angle of inclination        produced by the angle of slope sensor 27 is greater than a        positive threshold value registered in a suitable register and        representing the limit of “descent in reverse gear”;    -   a third AND gate for combining the output signals of the circuit        for activating the starting operation “on descent in reverse        gear” and of the circuit for detection of “descent in reverse        gear”;    -   a fourth AND gate for combining the output of the third AND gate        and the output of the circuit for testing the value of the        transmitted torque estimation ECT coming from the rest of the        starting device of the invention at a threshold value        ECTthreshold and for producing a release command of the        Automatic Parking Brake “on descent in reverse gear”.

In another embodiment, the vehicle being provided with a sensor formeasurement of the depression of the all-or-nothing clutch pedal, thesignal emanating from that sensor being at “1” when the clutch is open,“idling” of the vehicle is thus directly detected without the need totest the different situations in which the power unit has been separatedfrom the driving wheels.

In another embodiment the method of the invention also involves a stageof detection of excess pitch. In a first application, the pitch sensormakes it possible to detect that, when the vehicle accelerates, thebrakes are still locked and, therefore, to confirm in a subsequent stagea release command of the automatic parking brake. In a secondapplication, the stage of detection of a pitch value is followed by astage to prevent release of the Automatic Parking Brake in a startingposition, if the pitch of the vehicle applied, for example, by too greata movement of the passengers of the vehicle exceeds a certainpredetermined threshold.

For that purpose, the device of the invention contains a circuit fordetecting excess pitch, the output of which is active if the excesspitch exceeds a threshold predetermined in a register. The output of thecircuit for detecting excess pitch is combined by a reversing input ofan AND gate, another input of which is connected to the output of thedevice previously described, on which is located the release command ofthe Automatic Parking Brake, and the output of the AND gate producingthe release command of the Automatic Parking Brake outside of excesspitch.

The circuit for detecting excess pitch contains an input terminal thatreceives a signal produced by the angle of slope sensor 27, whichpresents sufficient resolution for detecting excess pitch. The angle ofinclination detection signal is transmitted to the input of a circuitfor producing a signal representing the time derivative of the angle ofinclination detection signal, the output of which is connected to aninput of a comparator, the other input of which is connected to aregister maintaining an excess pitch threshold value. The output of thecomparator is active when the derivative of the signal representing theangle of inclination of the sensor 27 is greater than the predeterminedthreshold.

In one embodiment, the excess pitch threshold value is produced by agenerator of excess pitch threshold values as a function of the angle ofinclination produced by the sensor 27.

In another embodiment the generator of excess pitch threshold valuescontains a first series of threshold values in a first startingdirection and a second series of threshold values in a second startingdirection.

The method of the invention also makes it possible to provide anoperation of anticipation of the dynamics of starting. For that purpose,the method of the invention also includes a stage for determining a termof anticipation on the starting command of the Automatic Parking Brakeas a function of predetermined anticipation values.

For that purpose, the method of the invention consists, upon executionof the method of elaboration of the release command of the AutomaticParking Brake already described, in also executing a stage ofmeasurement of the degree of depression of the accelerator pedalTheta_Acc, then measuring a time derivative of the signal Theta_Acc ofthe degree of depression, that is, D_Acc, and comparing thatinstantaneous value of derivative D_Acc with a predetermined thresholdThreshold_Anticipate, so that if the rate of variation of the degree ofdepression D_Acc is greater than a Threshold_Anticipate value, theincrementation loop of the transmitted torque estimation value ECT willbe interrupted before the test 33 (FIG. 2) is true and in order toproduce in advance the Automatic Parking Brake release command.

The device for use of the method of invention contains for that purposea circuit for calculating the time derivative D_Acc of the signalTheta_Acc of the degree of depression supplied by the angle of slopesensor 27 (FIG. 1). The circuit for calculation of the derivative D_Acccontains an output which is connected to a first input of a comparator,the other input of which is connected to a generator of a predeterminedThreshold_Anticipate value, so that its output is active if theThreshold_Anticipate value is exceeded. The output signal of thecomparator is then transmitted to a first input of another AND gate, thesecond input of which is connected to a circuit for detecting that thetransmitted torque estimation ECT is in the process of incrementation,for example, by detecting the evolution of the counter CPTR (83, FIG.6). The output of the other AND gate is then used as anticipated releasecommand of the Automatic Parking Brake.

In one particular embodiment, the predetermined thresholdThreshold_Anticipate is a predetermined function dependent on the degreeof slope measured by the angle of slope sensor 27 (FIG. 1).

The device for use of the invention contains for that purpose agenerator of a predetermined threshold Threshold_Anticipate in the formof a table of threshold values addressed by the value of the degree ofslope measured by the angle of slope sensor 27. The Threshold_Anticipatevalue is then transmitted to the aforementioned comparator of the deviceof the invention.

In an embodiment of the method of the invention, the operation ofanticipation of the dynamics of starting also involves a stage fortaking into account the response time of the electric motor equippingthe Automatic Parking Brake as well as the different movements in thebraking mechanism it activates.

In the method of the invention an anticipation of starting of theparking brake is provided for in order to take into account the dynamicsof the driver and the response time of the electromechanical system. Theresponse time of the electromechanical system is known through previousmeasurements and, if necessary, with a calibration procedure. Let Tr bethe response time. At each instant the transmission torque estimationECT and its time derivatives, like (d/dt)·ECT, are determined. Thosetime derivatives make it possible to take into account the driver'sdynamism, the value of the first time derivative increasing with thedriver's dynamism. According to the invention, a prediction stage isexecuted by extrapolation. In one embodiment an extrapolation orprediction is then made on the prediction value of the transmittedtorque estimation by an equation of the form (at order 1):ECT_predicted(Tr)=ECT+Tr×(d/dt)·ECT.

In order to make a prediction, an operator must therefore receive oninputs:

-   -   a characteristic value of response time Tr registered, for        example, in a suitable memory calibrated, if need be, by a        response time processor of the automatic parking brake system;    -   at least one value in the course of a transmitted torque        estimation ECT_current.        The operator then includes a derivator which contains in known        manner:    -   a memory of a preceding acquisition of a transmitted torque        estimation ECT_old and, in one particular embodiment, a memory        of a time coefficient Ta proportional to the time separating two        acquisitions or transmitted torque estimations;    -   a subtractor for carrying out the operation ECT_current−ECT_old;    -   a divisor for carrying out the time derivation proper through an        operation of the form (ECT_current−ECT_old)/Ta.        The operator also includes:    -   a multiplier, of which one input is connected to the memory of        the response time Tr and the other input is connected to the        output of the divisor producing the value (d/dt)·ECT and the        output of which produces the value Tr×(d/dt)·ECT;    -   an adder for carrying out the operation        ECT_predicted(Tr)=ECT_current+Tr×(d/dt)·ECT.        The anticipation can then, according to the method of the        invention, be carried out by execution of a test, the threshold        of which, S_min_predicted and/or S_max_predicted, is        predetermined. Such a test is in the form:        S_min_predicted<ECT_predicted<S_max_predicted, so that if the        test is positive, an anticipated release command of the        automatic parking brake is generated on output of the control        computer 5 of the Automatic Parking Brake.

The device of the invention for using the method of the inventioncontains at least:

-   -   one memory of a threshold value S_min_predicted and/or        S_max_predicted of anticipation release test for registering in        fixed or calibratable manner as a function of a calibration        processor of starting anticipation thresholds;    -   one comparator of the output value of the aforementioned        operator in order to make a prediction on the engine torque        estimation value to at least one of said threshold values        S_min_predicted and/or S_max_predicted, so that an anticipated        release authorization signal to the Automatic Parking Brake will        be produced if the comparator is activated.

In one embodiment the device of the invention consists of a processorwith a logic architecture in four blocks, namely:

-   -   an acquisition block of input data, among which are the engine        speed Wm, the speed of the vehicle Vv, the angle of slope, the        estimated average torque Cme, and the degree of depression of        the accelerator pedal THETA_Acc, notably sampled on the CAN 1        bus;    -   a signal treatment block applied to input data, particularly        carrying out digital filtering of all or part of the input data        and making scale or unit corrections;    -   a block for initialization of the parameters of the method of        the invention, involving notably the threshold values and        initializations of the counters;    -   a block for execution of the method in order to generate a        release command of the Automatic Parking Brake.

1. A method of assistance in starting a vehicle including a power unitand an automatic parking brake equipped with a mechanism of executing acommand to release or deactivate the automatic parking brake,comprising, at least after one starting phase of the power unit:estimating a transmitted torque value required to balance the vehicle ona slope; executing in a loop an incremental calculation comprising:reading an effective average torque value (Cme) associated with adynamic stage of the power unit, reading an engine speed value (Wm),calculating a time derivative of the engine speed, determining a momentof inertia of the power unit (Jmot) and calculating a load moment in aform of a product of the moment of inertia of the power unit by the timederivative of the engine speed, and determining an estimation of torqueactually transmitted at a given moment (ECT) according to an equation:ECT=Cme−Jmot×dWm/dt, wherein the loop is executed while the estimationof the torque actually transmitted is insufficient to surpass theestimation of the transmitted torque required to balance the vehicle onthe slope; and after the executing, producing a starting or deactivationcommand of the automatic parking brake.
 2. A method according to claim1, further comprising resynchronizing the reading the effective averagetorque value and the reading the engine speed value, so that each pairof the values corresponds to a same time interval.
 3. A method accordingto claim 2, further comprising adding a predetermined delay, equal tothree periods of passage to a Top Dead Center of a thermal engine of thepower unit, on a value of the resynchronization of the estimated averagetorque value, to take into account a waiting time for filling of amanifold and for ignition.
 4. A method according to claim 2, wherein theresynchronization includes applying the resynchronization on derivativevalue (D_Wm) of the engine speed (Win) between two samples separated bya resynchronization time according to equation: D_Wm=[Wm(8)−Wm(1)]/time,in which time determines a resynchronization period and Wm(1) and Wm(8)values of beginning and end of a resynchronization period.
 5. A methodaccording to claim 1, wherein the estimating the transmitted torquerequired to balance the vehicle on the slope comprises: comparing theestimation of the transmitted torque required to balance the vehicle onthe slope to a predetermined threshold value; if the predeterminedthreshold value is exceeded, testing an output value of a counter,incremented on each transmitted torque estimation stage relative to thepredetermined threshold value, if the predetermined threshold value isexceeded, producing a command authorizing release of the automaticparking brake.
 6. A method according to claim 5, wherein the estimatingthe transmitted torque required to balance the vehicle on the slopefurther comprises executing a predetermined offset, so as to reduce adisturbing effect of starting and/or stopping of some secondaryconsumers of energy or power supplied by a thermal engine, by carryingout the operation:ECT _(—) Corr _(—) k=ECT _(—) k+g(Consumers), to determine a range inwhich the engine can be considered idling and a range during which anoffset on the estimating the transmitted torque can be executed.
 7. Amethod according to claim 6, wherein the executing the offset is carriedout following a test in a course of which four conditions are combined:Wm≦Smax_Wm_Idle,ABS(D _(—) Wm)≦Smax_(—) D _(—) M_idle,THETA_Acc≦Smax_acc_idle,D_Acc≦0, conditions under which: Smax_Wm_idle represents a thresholdvalue below which the engine speed indicates that the engine is at restor idling; Smax_D_M_idle represents a threshold value below whichabsolute value ABS(D_Wm) of the time derivative of the engine speed D_Wmindicates that the engine is at rest or idling; Smax_acc_idle representsa threshold value below which degree of depression of the acceleratorpedal THETA_Acc indicates that the engine is at rest or idling; D_Accrepresents time derivative of the degree of depression THETA_Acc of theaccelerator pedal, which is negative when the driver lifts a foot fromthe accelerator pedal; so that, if the test is negative, the controlreturns to initialization of a counter, the power unit being deemedunconnected to driving wheels of the vehicle; and so that, if the testis positive, the control determines whether the counter is below apredetermined threshold value; so that if the counter is below thepredetermined threshold value, an initially zero offset value, when thecounter is initialized at the stage, is increased by a value of thecurrent estimation of the transmitted torque; then, the value of thecounter is incremented by one step, and the control is returned to thetest; and so that, if the counter is not below the predeterminedthreshold value, the offset value is transmitted to a routine ofcalculation of an offset value of the transmitted torque estimation, anoffset value noted offset_ECT which is equal to a ratio of the offsetvalue calculated to the value CPTR_threshold of the counter.
 8. A methodaccording to claim 1, further comprising producing a driver activityreport, so that release of the automatic parking brake will be refusedin case of lifting of an accelerator pedal of the vehicle.
 9. A methodaccording to claim 1, further comprising saturation detection of ahigh-speed thermal engine of the vehicle, so that release of theautomatic parking brake is prevented on saturation.
 10. A methodaccording to claim 1, further comprising an excess pitch detecting forpreventing release of the automatic parking brake in a startingsituation if the pitch of the vehicle exceeds a certain predeterminedthreshold.
 11. A method according to claim 1, wherein the estimating ofthe transmitted torque required to balance the vehicle on the slopeincludes calculating a static model of the vehicle on the slope from ameasurement of an angle of inclination delivered by a slope sensor andknowledge of a given value representative of a transmission speed.
 12. Amethod according to claim 11, wherein when the measurement of the angleof inclination is less than a given threshold, the estimation of thetransmitted torque required to balance the vehicle on the slope isincreased by a given value.
 13. A method according to claim 12, whereinthe given value of increase of the estimation of the transmitted torquerequired to balance the vehicle on the slope depends on the measurementof the angle of inclination.
 14. A method of assistance in starting avehicle including a power unit and an automatic parking brake equippedwith a mechanism of executing a command to release or deactivate theautomatic parking brake, comprising, at least after one starting phaseof the power unit: estimating a transmitted torque value required tobalance the vehicle on a slope; executing in a loop an incrementalcalculation of an estimation of torque actually transmitted at a givenmoment, while the estimation of the torque really transmitted isinsufficient to surpass the estimation of the transmitted torquerequired to balance the vehicle on the slope; after the executing,producing a starting or deactivation command of the automatic parkingbrake; and detecting a release demand when the power unit is notengaged, wherein the detecting includes, without using any sensor ofdepression of a clutch pedal of the vehicle, detecting an engaged stateby two maps of the estimation of torque transmitted as a function of adegree of depression of an accelerator pedal of the vehicle respectivelyestablished when wheels of the vehicle are engaged and when the wheelsare disengaged, and comparing the value of the estimation of torquetransmitted to each map value addressed by measurement of the degree ofdepression of the accelerator pedal to produce, if comparison to thefirst map is positive, a characteristic report of a disengaged state,and if the comparison to the second map is positive, to produce acharacteristic report of an engaged state.
 15. A method of assistance instarting a vehicle including a power unit and an automatic parking brakeequipped with a mechanism of executing a command to release ordeactivate the automatic parking brake, comprising, at least after onestarting phase of the power unit: estimating a transmitted torque valuerequired to balance the vehicle on a slope; executing in a loop anincremental calculation of an estimation of torque actually transmittedat a given moment, while the estimation of the torque really transmittedis insufficient to surpass the estimation of the transmitted torquerequired to balance the vehicle on the slope; after the executing,producing a starting or deactivation command of the automatic parkingbrake; and detecting idling speed, including: comparing information onestimated engine torque (Cme) to two functions of estimation of theidling speed in rotation with an estimation of positive transmittedtorque fp( ) and in rotation with an estimation of negative transmittedtorque fn( ), applying to the function fp( ) an idle gain applied on theestimated engine torque, an offset on the estimated engine torque valuein an idle position, and the estimated engine torque to produce anidling speed value in rotation with an estimation of positivetransmitted torque, applying to the function fn( ) an idle gain appliedon the estimated engine torque, an offset on the estimated engine torquevalue in an idle position, and the estimated engine torque to produce anidling speed value in rotation with an estimation of negativetransmitted torque, comparing an engine speed value to determine whethera positive or negative idling speed is present, on rotation with anestimation of positive transmitted torque or with an estimation ofnegative transmitted torque, and authorizing release of the automaticparking brake only if no idling speed is detected.
 16. A method ofassistance in starting a vehicle including a power unit and an automaticparking brake equipped with a mechanism of executing a command torelease or deactivate the automatic parking brake, comprising, at leastafter one starting phase of the power unit: estimating a transmittedtorque value required to balance the vehicle on a slope; executing in aloop an incremental calculation of an estimation of torque actuallytransmitted at a given moment, while the estimation of the torque reallytransmitted is insufficient to surpass the estimation of the transmittedtorque required to balance the vehicle on the slope; after theexecuting, producing a starting or deactivation command of the automaticparking brake; and producing a horizontal starting operation without athreshold on pressing an accelerator pedal of the vehicle, including:producing a parking brake release command on sole determination that theestimation of the torque actually transmitted is higher than apredetermined threshold and without testing the threshold on pressingthe accelerator pedal, initializing a starting state variable onstarting up the vehicle, to indicate that the accelerator pedal has notyet been depressed, to 0, reading a rest variable representative of astate of rest of an engine of the vehicle, treating a stabilizing statevariable so that the variable stays at 1 as soon as the accelerator hasbeen pressed and until an idle variable returns to 1, and thenauthorizing horizontal starting when the starting state variable equals0 and testing that the estimation of the torque actually transmitted ishigher than the predetermined threshold value to authorize release ofthe automatic parking brake and thus ensure starting of the vehiclekeeping the vehicle in a certain range of acceleration.
 17. A methodaccording to claim 16, further comprising extending the horizontalstarting operation to a descending starting operation in first gear. 18.A method according to claim 16, further comprising extending thehorizontal starting operation to a descending starting operation inreverse gear.
 19. A method of assistance in starting a vehicle includinga power unit and an automatic parking brake equipped with a mechanism ofexecuting a command to release or deactivate the automatic parkingbrake, comprising, at least after one starting phase of the power unit:estimating a transmitted torque value required to balance the vehicle ona slope; executing in a loop an incremental calculation of an estimationof torque actually transmitted at a given moment, while the estimationof the torque really transmitted is insufficient to surpass theestimation of the transmitted torque required to balance the vehicle onthe slope; after the executing, producing a starting or deactivationcommand of the automatic parking brake; and determining a term ofanticipation on the release command of the automatic parking brakedependent on predetermined anticipation values, which includes, uponelaboration of the automatic parking brake release command, alsoexecuting measuring a degree of depression of an accelerator pedal ofthe vehicle, and then measuring a time derivative of a signal of thedegree of depression, and comparing the instantaneous derivative valuewith a predetermined threshold, so that if the time derivative of thesignal of the degree of depression is greater than the predeterminedthreshold value, the incrementation loop of the estimation of the torqueactually transmitted is interrupted before the estimation of the torqueactually transmitted is sufficient to surpass the estimation of thetorque required to balance the vehicle on the slop, to produce inadvance the automatic parking brake release command.